<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>vw和vh</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        #banner{
            width: 89.3333vw;
            height: 38.4vw;
            margin: 25.87vw auto;
            background:#8ca;
        }
    </style>
</head>
<body>
    <!-- 
        375  3.75   1vw  3.75px
        vw vh 是两个长度单位
        1vw = 1% 的视口宽度
        1vh = 1% 的视口高度
     -->
    <div id="banner"></div>
</body>
</html>